GB2153520A - Method for quantitatively detecting the decarburization reaction in the production process of an electrical steel sheet - Google Patents
Method for quantitatively detecting the decarburization reaction in the production process of an electrical steel sheet Download PDFInfo
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- GB2153520A GB2153520A GB08431441A GB8431441A GB2153520A GB 2153520 A GB2153520 A GB 2153520A GB 08431441 A GB08431441 A GB 08431441A GB 8431441 A GB8431441 A GB 8431441A GB 2153520 A GB2153520 A GB 2153520A
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- 238000000034 method Methods 0.000 title claims description 41
- 238000006243 chemical reaction Methods 0.000 title claims description 28
- 229910000976 Electrical steel Inorganic materials 0.000 title claims description 27
- 238000004519 manufacturing process Methods 0.000 title claims description 14
- 238000005261 decarburization Methods 0.000 title description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 53
- 238000000137 annealing Methods 0.000 claims description 51
- 238000005259 measurement Methods 0.000 claims description 14
- 238000010521 absorption reaction Methods 0.000 claims description 10
- 230000001747 exhibiting effect Effects 0.000 claims description 5
- 229910052721 tungsten Inorganic materials 0.000 claims description 3
- 239000010937 tungsten Substances 0.000 claims description 3
- 239000004065 semiconductor Substances 0.000 claims description 2
- 229910052724 xenon Inorganic materials 0.000 claims description 2
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 claims description 2
- 239000007789 gas Substances 0.000 description 55
- 229910000831 Steel Inorganic materials 0.000 description 27
- 239000010959 steel Substances 0.000 description 27
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 17
- 229910052799 carbon Inorganic materials 0.000 description 17
- 238000001953 recrystallisation Methods 0.000 description 10
- 230000003287 optical effect Effects 0.000 description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 6
- 229910001224 Grain-oriented electrical steel Inorganic materials 0.000 description 5
- 229910052681 coesite Inorganic materials 0.000 description 5
- 229910052906 cristobalite Inorganic materials 0.000 description 5
- 229910052682 stishovite Inorganic materials 0.000 description 5
- 229910052905 tridymite Inorganic materials 0.000 description 5
- 238000005097 cold rolling Methods 0.000 description 4
- 238000001514 detection method Methods 0.000 description 4
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 229910000565 Non-oriented electrical steel Inorganic materials 0.000 description 3
- 238000007796 conventional method Methods 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- 235000012239 silicon dioxide Nutrition 0.000 description 3
- 102100021102 Hyaluronidase PH-20 Human genes 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 101150055528 SPAM1 gene Proteins 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 2
- 239000007795 chemical reaction product Substances 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 229940073577 lithium chloride Drugs 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 238000009628 steelmaking Methods 0.000 description 2
- -1 1.39 Lrn Chemical compound 0.000 description 1
- 230000005457 Black-body radiation Effects 0.000 description 1
- 229910017082 Fe-Si Inorganic materials 0.000 description 1
- 229910017133 Fe—Si Inorganic materials 0.000 description 1
- 229910000661 Mercury cadmium telluride Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 239000012671 ceramic insulating material Substances 0.000 description 1
- 239000010960 cold rolled steel Substances 0.000 description 1
- 230000006735 deficit Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000012625 in-situ measurement Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
- 238000002310 reflectometry Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D3/00—Diffusion processes for extraction of non-metals; Furnaces therefor
- C21D3/02—Extraction of non-metals
- C21D3/04—Decarburising
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/56—Investigating or analyzing materials by the use of thermal means by investigating moisture content
- G01N25/66—Investigating or analyzing materials by the use of thermal means by investigating moisture content by investigating dew-point
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- Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- Pathology (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
- Manufacturing Of Steel Electrode Plates (AREA)
Description
1
SPECIFICATION
GB 2 153- 520 A 1 Method for quantitatively detecting the decarburization reaction in the production process of an electrical steel sheet.
Background of the invention
Field of the invention
The present invention relates to a method for quantitatively detecting the decarburization reaction occurring in an annealing furnace during the production of an electrical steel sheet. More particularly, the 10 present invention relates to a method for in situ detection of the decarburization reaction which occurs in an annealing furnace.
Description of the related art
An electrical steel sheet is used forthe core of electrical machinery and devices. Electrical steel sheets are 15 largely classified into two types, i.e., a non-oriented electrical steel sheetwhich is produced by utilizing primary recrystallization and normal grain growth and a grain-oriented electrical steel sheet which is produced by utilizing a phenomenon in which crystal grains having a particular crystal orientation, e.g., the orientation expressed by the Miller index as 11 101<001 >, are caused to grow abnormally, this abnormal growth being referred to as secondary recrystallization.
Carbon is one of the impurities of a non-oriented electrical steel sheet and is removed or clecarburized during its production to as low a level as possible since the carbon remaining in the final product impairs the magnetic properties of the product and, with the lapse of time, the magnetic properties of the core in which the product is used gradually deteriorate. This deterioration is referred to as a magnetic aging phenomenon.
The carbon content of silicon steels can be decreased in the molten-steel processing stage including steelmaking and the pretreatment of molten steel. If it is attempted to attain in the molten-steel processing stage a low carbon content which is not detrimental to the magnetic properties, a sophisticated operation technique which is indispensable for attaining the desired carbon level renders the production efficiency at steelmaking very low. Therefore, some carbon usually remains in the molten-steel processing stage and is removed or decarburized at a later stage. This decarburization is usually carried out during the annealing stage, i.e., decarburization is attained together with primary recrystallization and normal grain growth during annealing.
In the production of a grain-oriented electrical steel sheet, a certain carbon content is necessary for realizing stable secondary recrystallization. Molten steel has, therefore, a carbon content of from approximately 0.02% to 0.06% so that such carbon content of a strip creates a condition for stable secondary 35 recrystallization.
The necessity of controlling the carbon content in the range above has long been known in the pertinent technical field.
Japanese Unexamined Patent Publication No. 58-55530 discloses a representative method for controlling the carbon content. In the method disclosed in this publication, the product is obtained by the following 40 processes: single pass cold-rolling of a hot-rolled strip or a multi pass of cold-rollings with intermediate annealing to otain the final thickness of the product; decarburizing annealing in a wet hydrogen atmosphere; applying and then drying powder mainly composed of MgO; and subsequently annealing at a temperature exceeding 11 OO'C. The aims of this annealing carried out at the final production step are to generate secondary recrystallization and to form a ceramic insulating material mainly composed of 2MgO'SiO2 due to 45 the reaction between Si02, which is formed on the sheet surface during the decarburizing-annealing step, and MgO, which is applied on the sheet surface. An aim of clecarburizingannealing is to reduce the carbon content of the steel sheet prior to secondary recrystallization annealing to as low as possible, usually 0.002% or less, thereby stably generating secondary recrystallization.
Conventionally, the decarburization of a hot-rolled steel sheet is carried out only in the clecarburizing- 50 annealing step. As is disclosed in Japanese Unexamined Patent Publication No. 58-5530 mentioned above, the optimum carbon amountfor secondary recrystallization depends on the carbon amount in the cold-rolling step. Therefore, according to a recently employed clecarburization method, clecarburization is carried out in the annealing step of a hot-rolled strip or in the intermediate annealing step so as to provide such a complete clecarburization as previously attained in the decarburizing annealing step.
In summary, no matter what kind of non-oriented or grain-oriented electrical steel sheet is to be produced decarburization is carried out by annealing.
Incidentally, decarburization proceeds, during the decarburizingannealing step, according to the following reactions: C(in Fe-Si) + 1120::2CO + H2. Since the amount of carbon in steel is great at the initial period of annealing, the amount of CO formed is great. If a considerable amount of CO is formed, the reaction mentioned above proceeds in the left direction or an oxide is formed on the surface of the steel sheet, with the result that the decarburization rate is retarded. In this case, it is necessary either to increase the H20 or to dilute the formed CO with a supplying gas medium in order to promote clecarburization. In an annealing period where decarburization proceeds and the carbon amount in steel is thus decreased, the amount of formed CO becomes low. In this case, unless the H20 amount in the gas annealing atmosphere is 65 2 GB 2 153 520 A 2 decreased, an oxide of high order isformed on the surface of the steel sheet. Itis accordingly necessaryto detect the H20 and CO amounts in annealing atmosphere and to control the annealing atmosphere depending upon the detected H20 and CO amounts. This control is effected by supplying gases into the annealing furnace or adjusting the dew point of the gas atmosphere of the annealing furnace. Such control is the strictest in the decarburizing-annealing step, which is carried out after the final cold-rolling step of 5 production of a grain-oriented electrical steel sheet, as is described in detail hereinafter.
The principal aims of decarburizing-annealing are to cause primary recrystallization of the cold-rolled steel sheet and decarburization, as well as to form a silica-scale layer, i.e., an oxide film. The silica-scale layer formed in the decarburizing-annealing step exerts great influences on the formation of a primary film, i.e., a forstellite film which is formed at a later step than the decarburizing- annealing step. The formation of a 10 silica-scale layer and its properties therefore play an important role in determining the power loss characteristics of the articles in which the grain-oriented electrical steel sheet is used.
The H20, which participates in the above-described decarburization reaction C + 1-120;_-CO + H2 and which is brought into reaction with the carbon in steel, is the water vapor contained in the gas atmosphere of the annealing furnace. In the decarburizing-annealing step, clecarburization by H20 first occurs. If, however, the 15 H20 partial pressure is too high, a film of oxides, such as FeO, Fe203, and the like, is formed on the surface of the steel sheet and impedes the contact between the H20 and C, thereby suppressing decarburization and hence impairing the magnetic properties.
The H20 then reacts with the Si contained in the steel in a later half period of the decarburizing-annealing step and causes the formation of a silica-layer scale, Le, a film of oxides, such as Si02,2FeO'SiO2, and the 20 like, according to the following reactions:
Si + 2H20 ---" Si02 + 2H2 2Fe + Si + 4H20 - 2FeCSi02 + 4H2 If these reactions proceed to the extent of excessive oxidation, the adhesiveness of the film is impaired and the film thickness exceeds that of requisite primary film, resulting in a reduction in the space factor of a core and impairment of the film properties. Oxidation by the above reactions should be controlled to provide the oxide film with an amount and composition appropriate for forming a primary coating having an excellent 30 quality since the amount and composition of the oxide film exerts an influence on the quality of glassy insulating film mainly composed of 2MgO'SiO2 and referred to as the primary coating.
As is described above, both the decarburization reaction and the oxidation reaction for forming an oxide layer occur in the decarburizing-annealing step.
To attain compatible satisfactory decarburization and appropriate formation of the oxide layer, it is 35 important that the gas atmosphere, dew point, time, and the like of decarburizing-annealing be delicately controlled.
Conventionally, the partial-pressure ratio PH201PH2 of the water vapor and hydrogen gas or the dew point of the gases of the annealing furnace is controlled, such as is disclosed in Japanese Examined Patent Publication No. 58-43,691. The partial-pressure ratio and the dew point are determined by measuring the 40 proportion of water vapor to hydrogen priorto admitting the supply gases into the annealing furnace.
Alternatively, as is described in "Steel Handbook IV, 3rd Edition", edited by the Japan Institute for Iron and Steel, page 561, a dew probe, in which the hygroscopic saturation characteristic of lithium chloride is employed, is attached to the annealing furnace, and the gas atmosphere of the furnace is sucked outside the furnace into the dew probe to measure the dew point. In this case, the gas atmosphere at a portion of the 45 furnace interior is used to measure the dew point. The so-detected values are not considered to provide true information on decarburization and oxide-film formation since the partial- pressure ratio and dew point undoubtedly greatly vary spatially within the huge space of the annealing furnace.
By "true information", the inventor means the state of the gas atmosphere in the neighbourhood of the steel sheet. The inventor understands the necessity of quantitatively recognizing decarburization including 50 the formation of an oxide film and occuring due to reactions between the surface of the steel sheet and water vapor present in the vicinity of the surface.
Since conventional methods for measuring the dew point and the like involve points to be improved, conventional decarburization-controlling methods cannot be said to be satisfactory. That is, since an appropriate method for obtaining true information has not heretofore been provided, decarburization control not based on true information has been carried out previously.
3 GB 2 153 520 A 3 Summary of the invention
The present inventor conceived the concept of utilizing an electromagnetic wave for measuring the dew point. The dew point measurement method involved in this concept is to pass an electromagnetic wave beam in the vicinity of an article in a furnace and measure the absorption of the electromagnetic wave by the water vapor within the furnace. By this process, the dew point in the vicinity of the article in the furnace can be measured. The above concept is applied in the process for producing an electrical steel sheet.
It is an object of the present invention to provide more useful information for the operation control of the decarburizing step of electrical steel sheet production than do conventional methods for measuring the gas atmosphere of an annealing furnace.
It is a specific object of the present invention to provide a method for measuring the concentration of water 10 vapor in the vicinity of the surface of a steel sheet where the decarburization reaction occurs.
It is another specific object of the present invention to provide a method for simultaneously measuring in the vicinity of the surface of a steel sheet where clecarburization occurs the concentration of water vapor and the concentration of CO gas, i.e., the reaction product.
It is a further specific object of the present invention to provide a method for measuring the partial 15 pressures of CO gas and water vapor or the partial-pressure ratio PH20/PCO.
The concentration of water vapor and/or CO gas, the partial pressures of water vapor and CO gas, the partial-pressure ratio PH20/PCO, or the dew point corresponding to the concentration of water vapor in the immediate vicinity of a steel sheet in an annealing furnace is measured by utilizing the fact that when an electromagnetic wave beam having a particular wavelength exhibiting an absorption characteristic due to 20 the water vapor and/or CO gas propagates in the furnace space, the absorption amount of the electromagnetic wave beam varies depending upon the amount of water vapor and CO gas.
Brief description of the drawings
Figure 1 is a drawing illustrating the measurement principle of the method according to the present 25 invention.
Figure 2 is a graph showing the relationship between the dew point and the pressure of saturated water vapor.
Figure 3 is a block diagram of the measurement system according to the present invention.
Figure 4 is a drawing illustrating an embodiment according to the present invention.
Figure 5 shows the result of a method according to the present invention for measuring the average dew point and the average CO gas concentration in the vicinity of a steel sheet in a continuous clecarburizing annealing furnace of an electrical steel sheet.
Description of the preferred embodiments
Referring to Figure 1, the fundamental elements of the present invention are shown.
A decarburizing-annealing furnace 1 is provided at both side walls 2, 2'with small apertures, which apertures are sealed by windows 3, 3' so as to prevent leakage of the gas atmosphere of the furnace interior.
The windows 3,3', which are transmissive to the electromagnetic wave, hereinafter referred to as electromagnetic wave transmissive windows 3,3'. An electromagnetic wave beam 5 is emitted from the 40 source 4, which is positioned, via the beam splitter7, opposite the electromagnetic wave-transmissive window 3. The wave-length band of the electromagnetic wave from the light source includes one or more bands absorbed by water vapor, such as 1.39 Lrn, 1.84 Lrn, 2.7 Lrn, and 5. 5 - 6.5 Lrn, and by CO gas, such as 4.6 - 4.7 pm. A detector 8 is positioned opposite the beam splitter 7. A reflection mirror 6, such as a Littrow reflector, is positioned outside the other electromagnetic wave- transmissive window 3'.
The electrical steel sheet 9 is positioned in the furnace interior 1' of the decarburizing-annealing furnace 1, and the surface 9' of the sheet is brought into an interface reaction with the water vapor in the furnace interior 1'.
The electromagnetic wave beam 5, e.g., an infrared ray beam, propagates so that it passes through the electromagnetic wave-transmissive window 3 and into the immediate vicinity of the surface 9'. The beam 5 50 is then reflected by the reflection mirror 6 and is again passed through the furnace interior 1'. The beam 5 is then reflected outside the furnace by the beam splitter 7 and is guided to the detector 8. The cross-sectional shape of the electromagnetic wave beam 5 can be optionally controlled by an optical technique but is preferably in the range of from 0.1 mm to 50 mm in diameter. The closer the distance between the beam 5 and the surface 9' of the electrical steel sheet, the more desirable is detection of the interface reaction.
However, since there are practical problems, such as vibration of the electrical steel sheet 9 travelling in the decarburizing-annealing furnace 1, the distance between the beam 5 and the surface 9' of the electrical steel sheet 9 is preferably not less than 0.1 mm and not more than 100 mm. The wavelength of the electromagnetic wave is selected, in accordance with the gas or gases to be detected, to be 1.39 Lrn, 1.84 Lrn, 2.7 pm, or 5.5 - 6.5 lim in the case of water vapor and 4.6 - 4.7 I. Lm in the case of CO gas. The intensity of 60 the electromagnetic wave detected by the detector 8 varies depending upon the concentrations of water vapor and CO gas formed due to the clecarburization reaction, and, therefore, the concentrations of water vapor and CO gas, the partial pressures of water vapor and CO gas, and/or the partial pressure ratio can be measured by the detector 8. This measurement is an in situ measurement of the furnace interior', where the decarburization reaction occurs.
4 GB 2 153 520 A 4 The passage of the electromagnetic wave beam 5 across the surface 9' of the electrical steel sheet 9 may be in any direction. When the electromagnetic wave beam 5 passes along the width of the electrical steel sheet 9 in the furnace interior 1', the average values of water vapor and/or CO gas over the width can be obtained, that is, the components which participate in the interface reaction are detected by their average value at a particular section of the decarburizing-annealing furnace 1. This makes it possible to control the decarburization process and material qualities by a method which is completely different from the conventional control methods for a decarburizing-annealing furnace for the production of an electrical steel sheet. In addition, since the detection of the electromagnetic wave beam 5 can be carried out at a high speed, continuous measurement is always possible even when the electrical steel sheet 9 travels in the furnace 10 interior 1' ata high speed.
The measurement principle according to the present invention is now described.
An infrared ray with a wavelength (k) exhibiting an absorption characteriStiGtO water vapor is expressed as having an intensity [,,(Z) at a distance (Z). The intensity [,,(Z) is expressed according to the Lambert-Beer low by the following general formula:
1JZ) = Ijo) exp (-u,.n,,-Z) in which 1,(o) = intensity at Z = 0, i.e., the incidence intensity, n, = mole number of the water vapor per unit volume, and a, = the attenuation constant of an infrared ray to water vapor. When the distance from the light source 4to the reflection mirror 6 is expressed by, the propagation 25 distance L becomes 2( (L = 2). By substituting Z of theformula (1) with L, (1), 1,(L) exp (-u,.n,-L) W0) .... (2) 30 Both sides of the formula (2) are changed logarithmic terms, and the n,of formula (2) is transposed to the left side.
n, = 1 n "(L) (x,,-L I'm (3) Since aw and L of the formula (3) are constants, the mole number of the water vapor per unit volume (n,,) is obtained from the ratio of the detected intensity (1,(L)) to the incidence intensity (1,(0)).
The furnace space shown in Figure 1 is supposed to be an open system into which the moistened AX gas is supplied from outside to maintain a constant dew point therein and in which the pressure of the furnace interior is maintained at substantially 1 atmosphere. The relationship between the partial pressure of the water vapor P,, the furnace volume V, the mole number of the water vapor Nw, and the temperature of the 45 gas atmosphere in the furnace T(K) is established in the open system of furnace space as follows:
P,.V = M,-R-T (4) in which R is the gas constant.
Since the mole number of the water vapor per unit volume (nw) is Nw/V, Pw can be expressed as follows:
P,, = n,-R-T .... (5) That is, when the mole number of the water vapor per unit volume (nw) is measured according to the formula (3) and when T is determined by the furnace temperature, the partial pressure of the water vapor Pw in the furnace interior can be obtained by the formula (5).
In addition, since the relationship between the pressure of saturated water vapor corresponding to (Pw) 60 and the dew point t, ('C) has the uniqueness shown in Figure 2, Pw leads to the determination of the dew point t,, ('C).
GB 2 153 520 A 5 Similarly, the mole number of the CO gas per unit volume of the furnace gas (nco) and the partial pressure of the CO gas (Pco) are given by the following formulas:
1 COL nco = tnL- a.co.L lco(O) and Pco = nco.R.T in which lco(O) = the incidence intensity at Z = 0 of an infrared ray, the wavelength of which is absorbed by the CO gas, lco(z) = the incidence intensity at a distance Z of an infrared ray, the wavelength of which is absorbed by the CO gas, and aco = the attenuation constant of an infrared ray, the wavelength of which is absorbed by CO gas.
The formula (8) is obtained by the formulas (3) and (6), and the formula (9) is obtained by the formulas (5) and (7).
(6) 5 (7) 10 nw aco L(L) ICO(L) tn-""' Wn ( nco (xw IM0) lcom P, nw Pco nco (9) The formula (9), in which the ratio of the partial pressure of water vapor, which causes the interface reaction, and the partial pressure of CO gas, which is the reaction product, are given, is a particulary appropriate formula to be used as an index of the reaction state of decarburization.
Referring to Figure 3, a block diagram of the measurement system is shown.
Referring to Figure 4, an embodiment, in which the present measurement principle is applied, is shown.
The electromagnetic wave beam 5 from the light source 4 has a wavelength band including the wavelength X exhibiting the property of absorption by water vapor. Only this wavelength X is passed through the filter 10. The electromagnetic wave beam 5 passed through the filter 10 arrives first at the beam splitter 7 and then at the rotary sector 11. The rotary sector 11 includes completely transmissive window 1 V, a total-reflection mirror 1 V', and a total-absorption surface 11---. When the completely transmissive window 11' is positioned across the optical path of the electromagnetic wave beam 5 during the rotation of the rotary section 11, the beam 5 is emitted into and propagates in the furnace interior 1' and is reflected by the reflection mirror 6 along the previous optical path. The electromagnetic wave beam 5 is then reflected by the beam splitter7 and enters the detector 8. The signal so detected by the detector 8 is expressed by 11.
When the total-reflection mirror 1 V' is positioned across the optical path of electromagnetic wave beam 5, total reflection of the beam 5 occurs there. The reflected beam 5 is reflected by the beam splitter 7 and then enters the detector 8, which detects the signal 12.
When the total-absorption surface 11"' is positioned across the optical path, the signal which is reflected by the surface 11 and is then detected by the detector 8 is deemed to be zero level and is expressed by 13. 50 The above-described signals can be described as follows:
11 = k, lx (0) exp (-a,,'ZO - a,,L) + lb (10) 12 = k2 lX (0) exp (_Un'70) + lb 13 = lb (11) (12) The above k, and k2 are constant coefficients in which the reflectivity of mirrors and geometrical constants of the optical system are included. The above n' is the optical distance from the rotary section 11 via the beam splitter 7 to the detector 8. The above lb is a detected noise value including the noise from the ambient 65 background color.
6 GB 2 153 520 A 6 (11 - 13M12 - 13) is obtained from the following formulas (10) - (12):
11 - 13 = ki exp (-ot,, L) (13) 12 - 13 1(2 5 Theformula (14) is obtained from thefollowing formula (13):
n = - 1 1 n (k 11 - 13) ot. L 12 - 13 (14) 10 in which k = k2/k, constant.
The mole number (n) of the water vapor per unit volume of the furnace interior (gas) is thus obtained from theformula(14).
A computing system connected to the detector 8 can perform the calculations as described above following the procedure shown in Figure 2 and can readily give the value of "n".
The method for measuring water vapor is described with reference to Figure 4. The method for measuring CO gas can be carried out similarly. Alternatively, both water vapor and CO gas can be measured simultaneously, provided that abeam having a wavelength absorbed by water vapor and abeam having a 20 wavelength absorbed by CO gas propagate along the same optical path.
The present invention is now explained by way of examples.
Example 1
Watervaporwas measured inthisexample by using the embodiment shown in Figure4.
Atungsten-halogen lampwas used asthe lightsource4.An interference filter having awavelength A of 1.39 [Lm and a half-width LX of 0.15 [Lm was used as the filter 10. The electromagnetic wave beam 5 had a diameter of 3 mm and propagated over the surface 9' of the steel sheet at a distance of 10 mm from the surface W. A germanium (Ge) infrared ray sensor was used as the detector 8.
The furnace interior Vwas an open system and was maintained at 82WC in terms of the temperature of the 30 gas atmosphere. A constant amount of N2 gas containing water vapor was supplied into the furnace interior I.
By the measurement of water vapor, the mole number of the water vapor per unit volume (n) was found to be 3.5 mole/M3. The partial pressure of the water vapor was obtained by the formula (5) as Pw 0.32 atm 240 mmHg. The dew pointt, - 70'C was obtained from Pw and the data of Figure 2.
For comparing the otained dew point with the one obtained by a method, the gases of the furnace interior 1'were sucked outside from the immediate vicinity of the surface 9'and then subjected to measurement of the dew point using a commercially available lithium-chloride dew point meter. The dew point measured by this meter was 71 C.
The dew point measured by the method of the present invention was virtually coincident with the one 40 measured by the conventional method. This fact verified the measurements of the mole concentration and the partial pressure of the water vapor according to the method of the present invention.
Example 2 45 CO gas was measured in this example by using the embodiment shown in Figure 4. A black-body radiator furnace having a temperature of 800'C was used as the light source 4. An interference filter having a wavelength X of 4.6 [Lm and a half-widthU of 0.1 [Lm was used as the filter 10. An HgCdTe infrared ray sensor was used as the detector 8. CO gas was supplied from a bomb into the furnace interior 1', maintained at a normal temperature, in such an amount that the mole concentration of the CO gas amounted to nco = 1.8 mole/m'.
The mole concentration was measured, using the formula (14), as nco = 1.9 mole/M3, which was close to the supplied mole concentration. The formula (7) was substituted for this value to obtain the partial pressure of the CO gas. Pco = 0.047 atm = 35.7 mmHg was obtained.
Example 3
The measurement devices used in Examples 1 and 2 were fitted to the side walls of a decarburizingannealing furnace for the production of electrical steel sheets so that the optical path was positioned 10 mm from the sheet surface and crossed perpendicular to the travelling direction of the steel sheet. The average dew point and average CO gas concentration in the vicinity of the sheet surface were continuously monitored for a long time period. The results are shown in Figure 5.
Figure 5 clearly shows the variation of the average CO gas concentration with time.
As is described hereinabove, particularly in the examples, the concentrations and partial pressures of the water vapor and the CO gas, as well as the partial-pressure ratio measured by the method of the present invention, enable quantitative detection, in situ, of the decarburization reaction occurring on the surface of an electrical steel sheet. During normal production of an electrical steel sheet, such as carried out in Example 65 7 GB 2 153 520 A 7 3, the variation in the concentration of the CO gas is slight, as shown in Figure 5. However, when the line speed and/or temperature are changed, any abnormal signal of the CO gas concentration due to such change can be detected by the method of the present invention and can be directly used to control the decarburization process, thereby restoring the process stability.
In addition to the halogen-tungsten lamp and black-body radiation furnace, other light sources, such as a 5 xenon lamp, a tungsten lamp, and a tunable LASER such as a semiconductor LASER or C02 LASER, can also be used. Furthermore, a microwave-emitting source can also be used as thelight source since wavelength band of the microwave exhibits an absorption property to water vapor and/or CO gas.
The method according to the present invention may be carried out at a plurality of points along the longitudinal direction of a decarburizing-annealing furnace or the travelling direction of a steel sheet so as to 10 accurately detect the progress of clecarburization or the interface reaction of an electrical steel sheet. An emitting source and receptor of an electromagnetic wave can be installed on the furnace walls or outside the furnace, thereby preventing the heat from the furnace interior from influencing the measurement. In this case, continuous measurement is stabilized in every way.
The method according to the present invention not only is used for quantitatively detecting the decarburization reaction of an electrical steel sheet but also can be readily applied for control of the dew point of the furnace interior regarding a radiant-annealing furnace of a stainless steel sheet and continuous annealing of a thin steel sheet.
Claims (7)
1. A method for quantitatively detecting a clecarburization reaction in the production of an electrical steel sheet, wherein an electromagnetic wave beam, which has a wavelength exhibiting a characteristic of being absorbed by water vapor and CO gas, is passed to within a vicinity of a surface of the electrical steel sheet positioned in a decarburizing-annealing furnace and an absorption amount of the electromagnetic beam absorbed by the CO gas, which is formed due to a reaction between said water vapor and said surface of the electrical steel sheet, is measured, thereby yielding the concentrations of said water vapor and said CO gas.
2. A method according to claim 1, wherein a partial pressure of said water vapor and a partial pressure of said CO gas are obtained from said concentrations of water vapor and CO gas, respectively, and, further, a ratio of said partial pressures is obtained.
3. A method for quantitatively detecting a clecarburization reaction in the production of an electrical steel sheet, wherein an electromagnetic wave beam, which has a wavelength exhibiting a characteristic of being absorbed by water vapor and CO gas, is passed to within a vicinity of a surface of the electrical steel sheet positioned in a decarburizng-annealing furnace and an absorption amount of the electromagnetic beam absorbed by the water vapor is measured, thereby yielding the concentration of said water vapor and then 35 the dew point is obtained from the water vapor concentration.
4. A method according to claim 1, 2, or 3, wherein said electromagnetic wave beam is passed along a width of the electrical steel sheet.
5. A method according to claim 1, 2, or 3, wherein, as an emitting source of the electromagnetic wave beam, one member selected from a group consisting of a lamp for emitting an infrared ray, particularly a 40 black body, halogen-tungsten lamp, a xenon lamp, an infrared ray-emitting LASER, particularly a semiconductor LASER emitting a variable wavelength infrared ray, a C02 LASER, and a microwave generator, particularly a Gunn diode, is used.
6. A method according to claim 1, 2, or 3, wherein an emitting source and a receptor of the electromagnetic beam are installed at side walls of the decarburizing- annealing furnace or outside the 45 decarburizing-annealing furnace.
7. A method according to claim 1, 2, or3, wherein a plurality of measurement devices of the electromagnetic wave beam are installed in the clecarburizing-annealing furnace.
Printed in the UK for HMSO, D8818935. 7 85, 7102. Published by The Patent Office. 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP58240678A JPS60131446A (en) | 1983-12-20 | 1983-12-20 | Method for measuring dew point in furnace |
| JP59009192A JPS60166846A (en) | 1984-01-20 | 1984-01-20 | Measurement of decarburizing reaction in electromagnetic steel plate manufacturing process |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8431441D0 GB8431441D0 (en) | 1985-01-23 |
| GB2153520A true GB2153520A (en) | 1985-08-21 |
| GB2153520B GB2153520B (en) | 1987-04-23 |
Family
ID=26343874
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08431441A Expired GB2153520B (en) | 1983-12-20 | 1984-12-13 | Method for quantitatively detecting the decarburization reaction in the production process of an electrical steel sheet |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4647319A (en) |
| BE (1) | BE901317A (en) |
| CA (1) | CA1235925A (en) |
| DE (1) | DE3446193A1 (en) |
| FR (1) | FR2556838B1 (en) |
| GB (1) | GB2153520B (en) |
| IT (1) | IT1177473B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4203166A1 (en) * | 1992-02-05 | 1993-08-12 | Erno Raumfahrttechnik Gmbh | IR spectroscopic gas analysis appts. - has internally reflective hollow spherical sample chamber |
| CN110832117A (en) * | 2017-07-13 | 2020-02-21 | 日本制铁株式会社 | Grain-oriented electromagnetic steel sheet and method for producing same |
| US11346005B2 (en) | 2017-07-13 | 2022-05-31 | Nippon Steel Corporation | Grain-oriented electrical steel sheet |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8609619D0 (en) * | 1986-04-19 | 1986-05-21 | Procal Analytics | Gas analysis |
| FR2676280B1 (en) * | 1991-05-10 | 1994-08-05 | Lorraine Laminage | DEVICE FOR MEASURING THE QUANTITY OF A CONSTITUENT CONTAINED IN A SAMPLE OF PRODUCT BURNED IN AN OVEN. |
| US5472520A (en) * | 1993-12-24 | 1995-12-05 | Kawasaki Steel Corporation | Method of controlling oxygen deposition during decarbutization annealing on steel sheets |
| FR2824130B1 (en) * | 2001-04-26 | 2003-12-12 | Air Liquide | PROCESS FOR CONTROLLING A PRODUCT PROCESSED IN AN OVEN AND AN OVEN PROVIDED WITH CONTOLE MEANS |
| FR2835613B1 (en) * | 2002-02-06 | 2004-10-01 | Air Liquide | METHOD AND DEVICE FOR DETERMINING THE CONCENTRATION OF CARBON IN LIQUID STEEL |
| US20050000596A1 (en) * | 2003-05-14 | 2005-01-06 | Ak Properties Inc. | Method for production of non-oriented electrical steel strip |
| FR2859468B1 (en) * | 2003-09-09 | 2006-02-17 | Air Liquide | METHOD FOR CONTROLLING GLASS FUSION IN THE AREA OF REFINING AN OVEN |
| FR2859467B1 (en) * | 2003-09-09 | 2007-03-02 | Air Liquide | METHOD FOR CONTROLLING GLASS FUSION IN OVEN |
| CN103134771A (en) * | 2013-02-02 | 2013-06-05 | 浙江大学 | Carbon monoxide (CO) concentration and visibility detector and detection method thereof |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2886478A (en) * | 1953-06-29 | 1959-05-12 | Honeywell Regulator Co | Method and control apparatus for carburizing ferrous objects |
| US2914434A (en) * | 1956-04-11 | 1959-11-24 | Harold L Snavely | Method for controlling atmospheres while heat treating steel |
| FR1402856A (en) * | 1963-12-03 | 1965-06-18 | Siderurgie Fse Inst Rech | Method and device for monitoring oxidation reactions during refining of a metal bath |
| JPS4955386A (en) * | 1972-04-27 | 1974-05-29 | ||
| JPS54160514A (en) * | 1978-06-09 | 1979-12-19 | Nippon Steel Corp | Decarburization and annealing method for directional electromagnetic steel plate |
| JPS55128530A (en) * | 1979-03-24 | 1980-10-04 | Nippon Steel Corp | Method and apparatus for controlling atmosphere of direct fire heating type deoxidizing furnace |
| US4288062A (en) * | 1979-08-09 | 1981-09-08 | Holcroft | Apparatus for control and monitoring of the carbon potential of an atmosphere in a heat-processing furnace |
| JPS5843691A (en) * | 1981-09-09 | 1983-03-14 | Nec Corp | Trunk circuit |
| JPS5932528B2 (en) * | 1981-09-26 | 1984-08-09 | 川崎製鉄株式会社 | Method for manufacturing unidirectional silicon steel sheet with excellent magnetic properties |
-
1984
- 1984-12-13 GB GB08431441A patent/GB2153520B/en not_active Expired
- 1984-12-14 CA CA000470214A patent/CA1235925A/en not_active Expired
- 1984-12-14 US US06/681,629 patent/US4647319A/en not_active Expired - Fee Related
- 1984-12-18 DE DE19843446193 patent/DE3446193A1/en active Granted
- 1984-12-19 BE BE0/214193A patent/BE901317A/en not_active IP Right Cessation
- 1984-12-20 FR FR8419557A patent/FR2556838B1/en not_active Expired
- 1984-12-20 IT IT24146/84A patent/IT1177473B/en active
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4203166A1 (en) * | 1992-02-05 | 1993-08-12 | Erno Raumfahrttechnik Gmbh | IR spectroscopic gas analysis appts. - has internally reflective hollow spherical sample chamber |
| CN110832117A (en) * | 2017-07-13 | 2020-02-21 | 日本制铁株式会社 | Grain-oriented electromagnetic steel sheet and method for producing same |
| US11186891B2 (en) * | 2017-07-13 | 2021-11-30 | Nippon Steel Corporation | Grain-oriented electrical steel sheet and method for producing same |
| CN110832117B (en) * | 2017-07-13 | 2022-01-07 | 日本制铁株式会社 | Grain-oriented electromagnetic steel sheet and method for producing same |
| US11346005B2 (en) | 2017-07-13 | 2022-05-31 | Nippon Steel Corporation | Grain-oriented electrical steel sheet |
Also Published As
| Publication number | Publication date |
|---|---|
| IT8424146A0 (en) | 1984-12-20 |
| FR2556838A1 (en) | 1985-06-21 |
| BE901317A (en) | 1985-04-16 |
| GB8431441D0 (en) | 1985-01-23 |
| FR2556838B1 (en) | 1988-10-21 |
| DE3446193C2 (en) | 1987-10-22 |
| IT1177473B (en) | 1987-08-26 |
| DE3446193A1 (en) | 1985-06-27 |
| US4647319A (en) | 1987-03-03 |
| CA1235925A (en) | 1988-05-03 |
| GB2153520B (en) | 1987-04-23 |
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Legal Events
| Date | Code | Title | Description |
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| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19971213 |